P1394: DIFFERENT DOSES OF ANTITHYMOCYTE GLOBULIN (ATG) AS PART OF THE PREPARATIVE REGIMEN IN HEMATOPOIETIC STEM CELL TRANSPLANTATION (HSCT)
Authors: S. Zhou, M. xiong, G. wang, W. ling, J. zhu
Journal: HemaSphere (2022)

Background: Antithymocyte Globulin (ATG) are often used as a component of the preparative regimen in allogeneic HSCT to reduce the incidence and severity of GVHD. However, the appropriate dose of ATG is yet unclear. Aims: The aim of the present study is to report comparing outcomes of patients who receiving allo-HSCT with different doses of ATG in their conditioning regimen. Methods: We retrospectively analyzed the clinical characteristics of 237 patients with AML or B-ALL who underwent allo-HSCT in our hospital from May 2013 to August 2019. The median age was 21.63 years (range: 1-69 years). The median disease course from diagnosis to transplant was 28 months (range: 13-42 months). 81 patients with acute leukemia in first complete remission were considered to have low-risk disease. All other 156 (65.8%) patients were placed in the high-risk. Thirty nine(16.5%) patients underwent a matched unrelated donor (MUD) HSCT. Others underwent a haplo-HSCT. The conditioning regimen was Ara-C/Bu/cyclophosphamide or fludarabine/ATG for person with AML, Ara-C/TBI/cyclophosphamide or fludarabine /ATG for patients with B-ALL. ALL the patients received different doses of ATG: 61 patients received rabbit ATG (Thymoglobulin, Genzyme) at a total dose of 6 mg/kg and 100 patients received 5mg/kg total dose ATG (Thymoglobulin) and 76 patients received total dose of 16mg/kg ATG(Fresebius S). We compared the aGVHD, cGVHD, relapse, and overall survival (OS) of the three groups. Results: All patients tolerated the pre-treatment well. The total implantation rate was 100%. The median time of neutrophil engraftment (14 days,14days,13.5days, respectively) and platelet engraftment(13 days, 13days, 12days, respectively) were not significantly different between the three groups.The incidences rates of grade I-II aGVHD in 5mg/kg ATG, 6mg/kg ATG and 16mg/kg ATG-F patients were 39%, 36% and 21%, respectively. The grade III-IV aGVHD rates of three groups patients were 16%, 6.5% and 9.2%, respectively. The incidence rates of cGVHD were 30% in 5mg ATG, 21.3% in 6mg ATG and 32.9% in16mg ATG-F.There was no significant difference in either incidence rates of aGVHD or cGVHD. Futher, there were no statistically significant differences in morbidity of CMV between 5mg ATG Vs 6mg ATG and 6mg ATG Vs 16mg ATG-F(39%Vs36.1%, 36.1%Vs21.1%), but incidence rate of CMV was statistically significant difference in 5mg ATG 39% Vs 16mg ATG-F 21.1%(P=0.011). The cumulative incidence of EBV and BK-virus associated hemorrhagic cystitis between the three groups were no statistically significant.During the median follow-up period of 19.31 months (range: 1-74 months), OS were 66% in 5mg ATG patients,68.9% in 6mg ATG patients and 56.6% in16 mg F-ATG group, respectively. And,the OS were not significantly different between three groups.The relapse rate of 16mg ATG-F patients were higher than 6mg ATG group(8.2%Vs21.1%), and it was statistically significant(P=0.038).But there was no difference with the 5mg ATG group. Summary/Conclusion: Our data showed that: ATG dose of 6 mg/kg group was associated with a similar proportion of GVHD, Viral infections, relapse, and (OS) as 5 mg/kg ATG.Hower,the incidence rates of relapse in 16mg ATG-F patients higher than 6mg ATG group, but similar with ATG dose of 5mg group. In the future studies, the correct dose and preparation of ATG should be further discussed through multi-factor analysis.